The present invention relates generally to the field of electrosurgery, and more particularly to surgical devices and methods which employ high frequency electrical energy to treat a patient's skin and subcutaneous tissue, including skin resurfacing procedures, such as procedures for selectively ablating a thin layer of surface tissue, such as the corneum stratum.
In early dermatology procedures, cosmetic surgeons often employed chemical peels and/or dermabrasion techniques to remove outer layers of the patient's skin to rejuvenate wrinkled skin or to remove skins disorders, such as acne, lesions, early skin cancer, etc. These dermabrasion and chemical procedures, however, are difficult to control, requiring great surgical skill. In addition, these somewhat inelegant techniques often cause excessive bleeding, collateral tissue damage and patient discomfort.
In an effort to overcome some of the limitations of dermabrasion and chemical peels, lasers have been developed for use in cosmetic surgery. Lasers have improved the accuracy of skin resurfacing procedures, and they have reduced collateral damage to the tissue surrounding and underlying the treatment site. In laser dermatology applications, a handpiece is typically used to guide the output of a laser to the patient's skin, and to form a laser spot of a desired size on the region of the skin which is to be treated. The handpiece is typically attached to one end of an articulated arm which transmits the output of a medical laser (such as CO2 or Er: YAG lasers) to the handpiece and allows the handpiece a wide range of motion.
Although initially encouraging, lasers suffer from a number of drawbacks in dermatology procedures. In the first place, laser equipment can be very expensive because of the costs associated with the laser light sources. Moreover, those lasers which permit acceptable depths of necrosis (such as excimer lasers, erbium:YAG lasers, and the like) provide a very low volumetric ablation rate, requiring numerous passes over the same treatment area which amounts to longer procedural times. In addition, erbium:YAG lasers generally do not provide effective hemostasis during the procedure, resulting in excessive bleeding which disrupts the surgeon's view of the treatment site. The CO2 lasers provide a higher rate of ablation and an increased depth of tissue necrosis than their erbium: YAG counterparts. On the other hand, CO2 lasers often create significant residual thermal injury to tissue at and surrounding the treatment site, which requires long healing periods for the patient. In addition, CO2 lasers are associated with much pain and, therefore, require a lot of anesthesia, which increases the cost and length of the procedure.
Monopolar electrosurgical instruments have been used to effect electro-dessication of abnormalities, such as lesions, skin tags, viral warts, pigment nevi, moles and skin cancer. For example, Conmed Corporation manufacturers a monopolar device, termed the Hyfrecator™ having a single active electrode at the tip of an electrosurgical probe. In these procedures, the skin abnormality is typically removed with a scalpel, and a low voltage is applied to the active electrode in contact with the target tissue to deliver electric current through the tissue and the patient to a dispersive pad or indifferent electrode. The voltage desiccates the remaining abnormal tissue, and coagulates severed blood vessels at the target site. The remaining tissue is then removed with a sponge or similar material. The voltage generally must be low enough to prevent charring and potential scarring of the underlying dermis.
These electrosurgical devices and procedures, however, suffer from a number of disadvantages. For example, conventional electrosurgical cutting devices typically operate by creating a voltage difference between the active electrode and the target tissue, causing an electrical arc to form across the physical gap between the electrode and tissue. At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue. This high current density causes cellular fluids to rapidly vaporize into steam, thereby producing a “cutting effect” along the pathway of localized tissue heating. This cutting effect generally results in the production of smoke, or an electrosurgical plume, which can spread bacterial or viral particles from the tissue to the surgical team or to other portions of the patient's body. In addition, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site.
Recently, a new less invasive procedure for treating skin has been developed, termed Micro-Dermabrasion. This procedure involves delivering fine crystal grains, typically corundum or aluminum oxide, through a handpiece onto the skin's surface, where the crystal grains remove dead and damaged skin cells and help to stimulate the growth of new collagen in the underlying skin. The crystal grains remove only the top superficial layer of dead skin cells, the stratum corneum, without causing significant damage to the underlying epidermis layer. The procedure has been used for treating demarcation lines and wrinkles, photo-damaged skin, acne, pigmentation, scarring, sun damaged skin and cancerous lesions.
While the early marketing studies of the Micro-Dermabrasion process have been promising, this new technology still has a number of shortcomings. For one thing, the crystal grains are difficult to remove once they are embedded into the skin, which has generated some health concerns. In addition, these crystals may often get into the patient's airways or eyes, causing sneezing or other discomfort during the procedure. Moreover, the crystals may scratch the skin or cause minor scarring or discoloration on the neck or darker skins. Finally, since this procedure does not involve the application of heat, it may not have any effect on the underlying collagen in the epidermis and the dermis. Thus, it may not reduce the underlying wrinkles or stimulate any new collagen growth, as claimed in the early marketing studies of this process.